The invention relates to a device for the air-free filling of receptacles, in particular of flexible bags having closable filling and extraction connecting pieces and also to a method for the air-free filling of such receptacles with such a device.
So that the greatest possible freedom from germs and also a high protection against oxidation can be ensured during the filling of liquid, pasty, powdery or granular materials, for example in the case of rapidly perishable foodstuffs and drugs, various filling techniques and numerous types of filling machines have been developed. Thus it is known from U.S. Pat. No. 4,120,134 to convey flexible bags, the bag portions to be filled of which are folded together under virtually air-free conditions, from a supply to a holding device which grips on the filling and extraction connecting piece of the corresponding bag and positions the latter at its connecting piece during the subsequent treatment. If the relevant filling and extraction connecting piece is provided with a closure cap, the latter is removed by a corresponding device and the open connecting piece is then set against the delivery orifice of a filling pipe. A pressure element designed in the manner of a rocker is located at the flexible bag portion surface area remote from the filling pipe and causes the bag material wall to be pressed against the bag-inner-side edge of the filling and extraction connecting piece. Therefore the bag cannot unfold before its product is introduced. When the filling pipe is placed on, the desired product can be incorporated into the flexible bag portion, which thereby inflates until the desired filling level is reached. After subsequent removal of the filling pipe, the filling and extraction connecting piece is closed by means of a closure cap and the filled bag is delivered from the filling station.
A series of further measures are known which supplement or modify the fundamental sequence described above. For example, bags can be used, the filling and extraction connecting pieces of which, in addition to or instead of the closure cap, are provided with a closure foil on their opening edge, so that the connecting-piece inner space is also free of air. When the filling pipe is placed on, its delivery orifice can pierce through such a closure foil before the filling operation is started. It is also known to evacuate the flexible bag and the connecting-piece inner space before the start of the filling operation. Following the filling operation, inert gas can be blown in through the filling pipe, so that as little air as possible can pass into the closure area, in particular during the time interval between the removal of the delivery orifice from the filling and extraction connecting piece and the attaching of the closure cap.
A device for the aseptic filling of containers is known from German Offenlegungsschrift No. 2,919,388, in which device the filling pipe, the holding device for the respective filling and extraction connecting piece of the container and the device for the removing and placing on of a closure cap are accommodated in an aseptic chamber which is closed on all sides except for a locating opening for the filling and extraction connecting piece. Consequently, these parts are under a continuous sterilizing agent mist, for example iodine mist, H.sub.2 O.sub.2 /acid mist, etc. These sterilizing agent mists, which are sprayed into the chamber in mist form with sterile-air pressure, keep the entire inner space and also the outer surfaces of the valve, the plug holding grips and the plug sterile, with a positive pressure always prevailing in the chamber during the filling of the product into the flexible bag.
With a similar device to the device described above, it is known from German Offenlegungsschrift No. 2,918,707 to fill so called "bag-in-box" packs of relatively large volume, with the flexible bag portion adapting to the walls of a carton or a box during filling. At the start of the filling operation, a pressure plate engaging from the underside of the flexible bag portion ensures that the bag being filled is lowered uniformly during the filling operation.
Although evacuation of the filling and extraction connecting piece can already take place with the filling pipe placed on, as is known, for example, from the device according to U.S. Pat. No. 4,120,134, these measures are still not adequate to be able to completely eliminate the ingress of air or germs into the filling and extraction connecting piece, above all before and after the filling of the desired product. Just the ingress of air into the delivery orifice and therefore into the inner space of the filling pipe during the transition from one filling operation to the next, despite a subsequent evacuation, can adversely affect product remains which are then filled along with the product. Nor does the design of a chamber (e.g. according to German Offenlegungsschrift No. 2,919,388) holding the entire filling area under positive inert-gas pressure represent a satisfactory solution, because the inert gas, immediately after opening of the closure cap, flows into the flexible bag and inflates the latter. As is apparent, this can cause dosage problems.